i) Field of the Invention
The present invention relates to a carrier immobilized with a microorganism or a microorganism immobilized carrier and a producing method thereof, and more particularly to a microorganism immobilized carrier, where a microorganism is immobilized on .beta.-chitin and a producing method thereof.
ii) Description of the Related Art
Recently, in the various industrial fields including the food industry, researches of a method for making a fermentation process continuous by using an immobilized microorganism obtained by immobilizing a microorganism on an insoluble high molecule polymer carrier have been developed. Also, researches relating to a microbial electrode composed of a combination of a carrier membrane immobilized with a microorganism and a variety of electrodes have actively been conducted.
When a microorganism is immobilized on a carrier in an industrial scale, the followings are required. That is, an immobilization operation is simple, the immobilized microorganism is kept to be stable for a long time, and the carrier to be used is porous and inexpensive. Further, when the microorganism immobilized carrier is used for a microbial electrode, it is necessary that a substrate permeability of the carrier is good and the carrier can be formed to a thin membrane.
However, in a conventional microbial immobilization, in many cases, a cross-linking processing or the like is required for the carrier, and a secondary deactivation can be unavoidable due to heat, organic solvents or the like in the cross-linking process.
On the other hand, chitin is a natural resource present in abundance, and it has proposed to use a chitin mold for a carrier for immobilizing an enzyme, as disclosed in Japanese Patent Publication Nos. Sho 56-00035, 53-10150.
In a conventional chitin mold preparation method, it is well-known to use the chitin isolated by treating the exoskeleton of the crustacea or insecta with hydrochloric acid and caustic soda, as disclosed in Japanese Patent Laid-Open Nos.Sho 61-53339, 61-64256, 61-111686, 61-129005 and 61-212302.
However, since the chitin obtained from the exoskeleton of the crustacea or insecta is an .alpha.-type chitin or .alpha.-chitin, the doping formation ability is bad, and as a result, the obtained carrier has only an insufficient strength. Further, when .alpha.-chitin is formed as a filmy carrier, a nonwoven fabric-like carrier is obtained and no thin membrane carrier can be formed. Hence, the .alpha.-chitin cannot be practically used for a carrier for immobilizing the microorganism.
Under such circumstances, in order to solve the above-described problems, the present inventors have earnestly made researches and have found that a chitin having a .beta.-type structure or .beta.-chitin obtained from cuttlefish pen (cuttlebone) among a lot of chitin raw materials, in particular, the .beta.-chitin obtained from squid pen of the Teuthoidea or Sepioidea order in the Mollusca phylum possesses superior characteristics as a carrier, and by immobilizing a microorganism on the .beta.-chitin, a microorganism immobilized carrier with high activity can be obtained to complete the present invention.